Non-planar low-pressure organometallic chemical vapour deposition (LP OMCVD) of InP and InGaAs was performed on patterned (100) semi-insulating InP substrates. The patterns were 15-mum-high long mesa ridges bounded by (110) and (1 (1) over bar0) quasi facets and (100) top surfaces. Growth rates and surface morphologies on the facets were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical microscopy. Both InP and InGaAs nucleated sufficiently on the facets. While InP layers were smooth, InGaAs nucleated through facetted trapezoidal islands. The mechanism of facetting is qualitatively discussed. The InGaAs facetting as well as accompanying roughness were partly suppressed at lower growth temperatures.